Inhibitory neurons play a critical role in normal information processing in the neocortex. Moreover, their dysfunction may contribute to the pathophysiology underlying certain disorders. To date, most of our understanding of the diverse functions of inhibitory neurons and their synapses has been revealed through studies of sensory cortices. My long range goal is to determine if dramatic regional differences in local inhibitory networks result in distinct inhibitory and network mechanisms in the neocortex. My work will specifically focus on the medial prefrontal cortex (mPFC) and ventral postrhinal cortex (vPOR), brain areas with remarkably few parvalbumin- (PV) expressing interneurons compared to sensory cortices. The PFC and POR are essential in cognitive control and visuospatial attention, respectively, and their lack of PV- interneurons could play a pivotal role in how these areas normally process information. There are three specific aims in this proposal: 1) To characterize and compare the local inhibitory networks within the mPFC and vPOR; 2) To dissect the cellular mechanisms underlying thalamocortical feedforward inhibition in the mPFC and vPOR ; 3) To determine the cellular mechanisms underlying gamma oscillations in the mPFC and vPOR. All my data will be compared to data I obtain from the primary somatosensory cortex (SI), a leading model for studying the structure and physiology of neocortical circuits. To address these aims I will use a combination of in vitro patch clamp techniques, various optogenetic approaches, quantitative histological methods, and multiple transgenic lines of mice to identify, select, and manipulate activity of specific neurons. My research will illuminate the basic physiology and diversity of neural circuits in the neocortex. It also may shed light on certain neuropsychiatric conditions in which inhibition is compromised.